The need for precise, minimally invasive, surgical interventions has resulted in the creation of methods of using computers in conjunction with advanced assistance devices to improve surgical planning and execution. Over the past decade, a variety of such Computer Integrated Surgery (CIS) systems have been developed, with resulting clinical benefits, largely for use in the fields of neurosurgery, laparoscopy, maxillofacial surgery and orthopaedics, as for instance described in the article by L. Joskowicz et al., entitled “Computers in imaging and guided surgery”, published in Computers in Science and Engineering, Vol. 3(5), pp 65-72, 2001.
CIS systems can potentially benefit many orthopaedic surgical procedures, including total hip and total knee replacement, pedicle screw insertion, fracture reduction, and ACL (Anterior Cruciate Ligament) ligament reconstruction. These procedures are ubiquitous and are performed in high volume in operating rooms worldwide. They generally involve rigid bone structures that image well, require preoperative planning, and employ instruments and tools, such as implants, screws, drills, and saws that require precise positioning. A number of CIS systems for such procedures are currently in use, such as those described in the book “Computer Assisted Orthopaedic Surgery (CAOS)”, edited by L. P. Nolte, and R. Ganz, published by Hogrefe and Huber (1999).
One technique used for fracture reduction is closed intramedullary nailing, and, according to the article by R. J. Brumback, “Regular and Special Features—The Rationales of Interlocking Nailing of the Femur, Tibia, and Humerus”, published in Clinical Orthopaedics and Related Research, Vol. 324, pp. 586-651, Lippincott-Raven (1996), it is probably the current routine procedure of choice for reducing fractures of the femur and the tibia. This procedure restores the integrity of the fractured bone by means of a nail inserted in the medullary canal. In most cases, the surgeon inserts lateral proximal and distal interlocking screws, to prevent fragment rotation and bone shortening. Preparation of the bone for distal locking has long been recognized as one of the most challenging steps in the procedure, at least according to prior art methods of performing the procedure. The procedure is performed under X-ray fluoroscopy, which is used to view the position of the bone fragments, the surgical tools and the implants used, in order to determine the position of the holes to be drilled for these screws. Numerous X-ray fluoroscopic images are required for this procedure, since the nail often deforms by several millimeters to conform to the bone canal shape, and the exact position of the distal locking nail holes cannot therefore be determined in advance. According to these prior art methods, the surgeon adjusts the entry point and orientation of the drill, to the best of his judgement and his interpretation of the X-ray images, by repeatedly alternating between anterior-posterior and lateral X-ray fluoroscopic views, such that the drill axis coincides as accurately as possible with the corresponding nail hole axis. Drilling proceeds incrementally, with each advance verified with a new pair of X-ray fluoroscopic images. Once the pilot hole passing through the distal locking nail hole has been drilled in the bone, the locking screws can be inserted and fastened.
Because of the nature of the procedure, depending very largely on the skill of the surgeon, a number of complications can arise, including inadequate fixation, malrotation, bone cracking, cortical wall penetration and bone weakening due to multiple or enlarged pilot holes. Furthermore, it has been reported in the article “Interlocking medullary nails—radiation doses in distal targeting” by S. Skejdal and S. Backe, published in Archives of Orthopaedic Trauma Surgery, Vol. 106, pp 179-181, 1987, that the surgeon's direct exposure to radiation per procedure, using these prior art methods, is 3-30 minutes, depending on the patient anatomy and the surgeon's skill. In general, something between about 30 and 50% of this time is spent on the distal locking process.
Many non-CIS devices have been developed for distal locking, even recently, such as that described by C. Krettek, et al, in the article “A mechanical distal aiming device for distal locking in femoral nails”, published in Clinical Orthopaedics, Vol. 384, pp. 267-275, 1999. Examples of such devices and procedures include proximally mounted targeting devices, stereo fluoroscopy, mechanical guides, and optical and electro-magnetic navigation systems that help locate the center of the distal locking nail holes. However, these devices and techniques generally have some disadvantages, for instance that they are only selectively applicable, may be cumbersome and difficult to use, may not be sufficiently accurate, and they thus fail to significantly reduce the likelihood of patient complications.
Fluoroscopy-based CIS navigation systems, such as those described by L. Joskowicz, et al., in the article “FRACAS: A system for computer-aided image-guided long bone fracture surgery”, published in “Journal of Computer-Aided Surgery”, Vol. 3(6), pp. 271-288, 1999, take the guesswork out of targeting. Such systems enhance, reduce, or altogether eliminate X-ray fluoroscopic images by replacing them with a virtual reality view in which the positions of the bone and the surgeon's instruments are continuously updated and viewed on-screen as they move, using tracking devices and three dimensional registration procedures. They can assist the surgeon in aligning the drill axis with the distal locking nail hole axis to an accuracy of about 1 mm and 1°. However, they do not provide any mechanical guidance for the hand-held drill, which can slip or deviate from its planned trajectory as the drilling proceeds. Thus, even using such prior art CIS navigation systems, the surgical outcome of the procedure is still dependent to an extent on the skill of the surgeon.
Robot-based CIS systems have been developed to assist the surgeon in implementing the preoperative plan by mechanically positioning and sometimes executing the surgical action itself. One such system is described by K. Cleary et al., in the article “State of the art in surgical robotics: clinical applications and technology challenges”, published in Journal of Computer-Aided Surgery, Vol. 6(6), pp. 312-328, 2001. The robots are either floor-standing industrial robots, adapted for use in the desired surgical application, or table-mounted custom-designed serial robots. Such robots are generally voluminous and heavy, despite the fact that in such surgical applications, they need to operate with relatively small workloads and work volumes. In such systems, bone immobilization or real-time dynamic tracking are important issues, since the relative configuration of the bone with respect to the robot must be known precisely at all times. This may complicate the registration procedure and may adversely affect the overall system accuracy.
There therefore exists a need in the field of orthopaedic surgery, for a system which overcomes the disadvantages of prior art systems, and enables the automatic alignment of tools required for the procedure, with the bones or inserts involved in the procedure, such that the procedure becomes less dependent on the skill of the surgeon, with a concomitant increase in the success rate of the procedure.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.